The purpose of the research is to determine the role of the hypothalamus in the control of secretion of the tropic hormones, ACTH, LH, FSH, TSH, and prolactin, by the anterior pituitary gland. The role of such biogenic amines as dopamine, norepinephrine, and serotonin and other indoles on the secretion of hypophysiotropic substances into hypophysial stalk portal blood will be investigated. The biogenic amines will be administered by one of the following routes: (1) by intraventricular injection, (2) by means of microelectrophoresis, (3) by micro-infusion, and (4) by infusion into the median eminence following canulation of superior hypophysial artery or into the anterior pituitary by cannulation of a hypophysial portal vessel. The median eminence will be examined as a membrane involved in the transport of substances from cerebrospinal fluid to hypophysial portal vessels. Secretion rates of hypophysiotropic substances will be determined by collecting pituitary stalk blood and determining the rate of secretion of luteinizing hormone releasing hormone and thyrotropin releasing hormone into portal blood using specific radioimmunoassays. By means of these experimental procedures, the hypothesis will be examined that cerebrospinal fluid is an important means of transference of hypophysiotropic substances from extrahypothalamic regions of the brain to the anterior pituitary gland.